Sen. Harry Reid of Nevada is one of the fiercest partisans among the Democrats he leads in the Senate, ever ready with a word of abuse and malignant vilification, spreading taint wherever he goes. Ferocity and partisanship come with the territory, talents invaluable in politics. The Republicans should find someone so eager for the fight.

But Harry, a master of the Senate rules, knows when and how to flout the rules. He has been called a congenital liar, like Hillary Clinton, with deceit and calumny bred in his bones. But that’s too kind. Harry’s lies are not congenital. They’re worse than that. They’re calculated. Not just the usual political fibs like, “If you like the health insurance plan you have now you can keep it,” or, “Read my lips: no new taxes.” Harry tells big ones, personal and intended to deal damage in the worst way.

Over the past weekend Harry and the Democrats were desperate to create a firebreak against the bombshell that FBI Director James Comey had uncovered something new in Hillary’s emails and he would reopen his investigation into suspected high crimes by the Democratic nominee. Harry wrote a note to Mr. Comey, thinking it would be a similar bombshell, accusing him of “sitting on explosive information” demonstrating a damaging connection between the Russians and Donald Trump.

“In my communication with you and other top officials in the national security community,” he wrote, “it has become clear that you possess explosive information about close ties and co-ordination between Donald Trump, his top advisers, and the Russian government — a foreign interest openly hostile to the United States, which Trump praises at every opportunity.”

Harry doesn’t say where such calumny comes from, only that “it has become clear” to him, if to no one else. This is from the same senator who said in the 2012 presidential campaign, from his constitutionally protected perch in the well of the Senate, safe from having to account for libel or slander, that Mitt Romney had not paid his federal income taxes in years. He said he knew this because someone close to Mr. Romney, or close to someone who might have been his barber, or his gardener, or someone his barber knew, had told an insider who told Harry. Or something like that. Harry’s lies are well sourced.

Long after the 2012 election, and still with constitutional protection from prosecution for bearing false witness, Harry admitted he had no “inside source.” Mr. Romney had paid his taxes. Harry just made it up.

Harry was a boxer when he was a young man, perhaps the source of his political pugilism. He failed to make a career of it because he had been admonished by referees so often for hitting below the belt and biting in the clinches that no one would agree to fight him. So said inside sources. Such an accusation goes to the question of character and basic character. Could it possibly be true? Well, who knows? Maybe somebody is just making it up 50 years after the fact. Harry would understand.